Prevalence and level of Escherichia coli O157 on beef trimmings, carcasses and boned head meat at a beef slaughter plant

This study investigated the prevalence and level of Escherichia coli O157 on samples of beef trimmings (n = 1351), beef carcasses (n = 132) and bovine head meat (n = 132) in a beef slaughter plant in Ireland. The survey also included an assessment of the prevalence of virulence genes in the E coli O157 isolates obtained. Samples were examined for the presence of E coli O157 by direct plating on SMAC-CT and by enrichnient/immunomagnetic separation (IMS) with plating of recovered immunobeads onto SMACCT agar. Presumptive E coli O157 isolates were confirmed by PCR targeting a range of genes i.e. vt1, vt2, eaeA, hlyA, fliC(h7) and portions of the rfb (O-antigen encoding) region of E coli O157. Enterobacteriaceae on head meat samples were estimated by direct plating onto Violet Red Bile Glucose agar. E. coli O157 was recovered from 2.4% (32/1351) of beef trimmings samples, at concentrations ranging from < 0.70-1.61 log(10)cfu g(-1). Of the 32 positive isolates, 31 contained the eaeA and hylA genes while 30/32 contained the fliCh7 gene and 31/32 contained vt1 or vt2, or both vt genes. E coli O157 was recovered from 3.0% (4/132) of carcass samples, at concentrations ranging from < 0.70-1.41 log(10) cfu g(-1). All of the carcass isolates contained the eaeA, hylA and fiC(h7) genes. E. coli O157 was recovered from 3.0% (3/100) of head meat samples, at concentrations of 0.7-1.0 log(10)cfu g(-1). All of the head meat isolates contained the eaeA, hylA, fliCh7 and W genes. No head meat isolates contained the vt1 gene. Head meat samples (n = 100) contained Enterobaeteriaceae, at concentrations ranging from 0.70-3.0 log(10) cfu g(-1). Overall, the qualitative and quantitative data obtained for E coli O157 on beef trimming samples in this study could be employed as part of a quantitative risk assessment model. (c) 2005 Elsevier Ltd. All rights reserved.